横截面积对燃烧室内压力振荡及NOx生成特性的影响

Effects of Cross-Sectional Area of Combustion Chamber on Characteristics of Pressure Oscillation and NOx Formation

关键词:  燃烧室  燃烧不稳定性  NO_x生成  大涡模拟

Key words:  Combustion chamber  Combustion instability  NO_x formation  Large eddy simulation

摘要:

为了研究燃气轮机燃烧室结构对其性能的影响，采用三维全可压缩大涡模拟方法分析了燃气轮机燃烧室横截面积对燃烧室内压力振荡及NO_x生成特性的影响规律。分析表明:增大横截面积加速了射流的衰减过程，流体的发散角增大，中心回流区的范围扩大，回流速度则有所降低。中轴线附近，正向流动区域的范围扩大。由于径向旋流器与预混段的结构保持一致，不同横截面积时，上游流场中的进动涡核结构相似。增大横截面积使得燃烧室内声学耗散作用增强，压力振荡的幅值有所降低，因此，采用较大的燃烧室横截面积有利于抑制燃烧不稳定性现象的发生。由于峰值温度均超过1800K时，增大横截面积所导致的温度下降抑制了NO_x的生成，有利于控制NO_x排放。

Abstract:

Effects of chamber cross-sectional area on the characteristics of pressure oscillation and NO_x formation inside a gas turbine combustion chamber were numerically studied using a fully three dimensional compressible Large Eddy Simulation approach to evaluate its impacts on the performance of combustion chamber. The numerical results show that increasing the size of the combustion chamber improves the attenuate process and divergence angle of jet flow which increase the magnitude of central recirculation zone and thus compress the return velocity in this region. The magnitude of region with positive velocity rises with the increasing of chamber size. Differences in the structure of precession vortex cores are not significant due to the same structure of radial swirler and pre-chamber. The acoustics dissipation process of combustion chamber increases with the increasing of combustion chamber size which compresses the pressure oscillations amplitude inside the combustion chamber and thus beneficial for compressing the phenomenon of combustion instability. The peak temperature of the flame is much higher than 1800K. Therefore， decrease of the peak temperature caused by larger combustion chamber size compress the formation rate of NO_x which is beneficial for controlling the NO_x emission.